Directional broadcasting method

ABSTRACT

The current disclosure is directed to broadcasting information among nodes in the network. More specifically, the current disclosure relates to directional networking among nodes in the network. The directional broadcasting system allows for a more efficient way to deliver broadcasting information among nodes where at least some of the nodes use directional antennas.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/242,340, filed on Oct. 16, 2015; the entire disclosure of whichis incorporated herein by reference.

BACKGROUND

Technical Field

Generally, the present disclosure relates to communication systems. Moreparticularly, the present disclosure relates to a method of directionalnetworking. Specifically, the present disclosure is directed to a methodof broadcasting information within a wireless network wherein at leastsome of the nodes within the system use directional antennas.

Background Information

Directional networking is a set of networking and related protocolsusing one or more directional antennas may be used (for example) in theimplementation of Mobile Ad-hoc Networks (MANET). Directional networkingis an approach to network and protocol design that focuses on radiodevices using directional antennas, as opposed to omni-directionalantennas. Directional networking has become popular in military systemswith examples being Future Combat Systems—Communications (FCS-C) andHighband Networking Radio (HNR), but more recently this type ofnetworking has started to find application in commercial systems such asIEEE 802.11 and 802.15.

Directional networking systems are often developed in support of MANETnetwork topologies but can also be applied in other topologies such aspoint to multi-point (PMP) or even point to point (PTP). Many networkingprotocols require the ability to broadcast information in certaincontexts. The term “broadcasting” is used herein to mean distributingdata to all nodes capable of hearing transmissions from all nodes thatare sending transmissions. Examples of when broadcasting might be neededinclude when sending a beacon to support discovery or sharing of routingand scheduling tables.

Currently known directional antenna systems tend to be very inefficientwhen broadcasting information relative to systems that broadcast withomni-directional antenna. Using an omni-directional antenna, a singletransmission will reach all nodes that are within communications rangeat once. However, with a directional antenna only a subset of nodeswithin communications range may be reached with a single transmission.Because of this, the broadcast must be broken down into multipletransmissions and repeated so that it will reach all nearby nodes.Depending on node distributions and antenna patterns, this method ofbroadcasting may take a very long time compared to usingomni-directional antenna. While one could include two antennas in thesystem (an omni-directional antenna and a directional antenna) and thenuse the directional antenna for unicast information and theomni-directional antenna for broadcast, this is not always feasible.

Other currently known systems use a second system with different systemparameters geared for broadcasting in order to coordinate thedirectional system. An example would be the use of a military “Link 16”radio with omni-directional antennas to share pointing parameters for adirection common data link (CDL) so as to instantiate a CDL link.However it is not always possible to include a second system purely forthe purpose of broadcasting information to support a directionalnetworking system.

SUMMARY

It has been recognized that an improved set of protocols to ensureefficient broadcast within a directional networking system is needed.

The current disclosure is directed to broadcasting information betweennodes in a network when at least some of the nodes use directionalantenna.

In one aspect, the present disclosure may provide a method ofbroadcasting information in a network comprising: providing a MobileAd-hoc Network (MANET) that includes nodes, wherein at least some of thenodes use directional antenna, starting a broadcast session by orderingthe nodes in the MANET by address (particularly by arranging the nodesin ascending address order); determining a total number of the nodes;partitioning the nodes into a first group of nodes and a second group ofnodes (particularly by placing lower address nodes in the first groupand higher address nodes in the second group; and transmittinginformation from each node in the first group of nodes to acorresponding node in the second group of nodes; and reversing thetransmission by transmitting information from each node in the secondgroup of nodes to a corresponding node in the first group of nodes.

In another aspect, the present disclosure may provide a method ofbroadcasting information in a network comprising: providing a MobileAd-hoc Network (MANET) that includes nodes, wherein at least some of thenodes use directional antenna; ordering the nodes in the MANET;determining a total number of the nodes; partitioning the nodes into afirst group of nodes and a second group of nodes; transmittinginformation from each node in the first group of nodes to acorresponding node in the second group of nodes; reversing direction oftransmitting by transmitting information from each node in the secondgroup of nodes to a corresponding node in the first group of nodes;verifying that all nodes in the first group of nodes have communicatedwith all nodes in the second group of nodes; permuting the first groupof nodes and the second group of nodes if all nodes in the first groupof nodes have not communicated with all nodes in the second group ofnodes; repeating the steps of transmitting information from each node inthe first group of nodes to a corresponding node in the second group ofnodes; reversing the direction of transmitting and verifying that allnodes in the first group of nodes have communicated with all nodes inthe second group of nodes until all nodes in the first group of nodeshave communicated with all nodes in the second group of nodes; andverifying that there is only one node in each of the first group ofnodes and each of the second group of nodes after the step of verifyingthat all the nodes in the first group of nodes have communicated withall of the nodes in the second group of nodes and then ending thebroadcasting session.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A sample embodiment of the present disclosure is set forth in thefollowing description, is shown in the drawings and is particularly anddistinctly pointed out and set forth in the appended claims.

FIG. 1 is an exemplary schematic view of a PRIOR ART Omni-MANET framestructure showing an infinite number of nodes and slots;

FIG. 1A is an exemplary MANET using a PRIOR ART Omni-MANET framestructure;

FIG. 1B is an exemplary schematic view of the PRIOR ART Omni-MANET framestructure having only four nodes and four slots;

FIG. 1C is an exemplary graphic view of a broadcast using the PRIOR ARTOmni-MANET frame structure of FIG. 1B;

FIG. 2 is an exemplary schematic view of a PRIOR ART directional-MANETframe structure showing an infinite number of nodes and slots;

FIG. 2A is an exemplary MANET using a PRIOR ART directional-MANET framestructure;

FIG. 2B is an exemplary schematic view of a PRIOR ART directional-MANETframe structure having four nodes and showing a directional broadcastfor the four nodes that requires twelve slots;

FIG. 3A is an exemplary schematic view of a broadcast using adirectional-MANET frame structure and method in accordance with anaspect of the present disclosure; where the frame structure isillustrated as having four nodes, six slots and two transmissions;

FIG. 3B is an exemplary graphic view of the broadcast between the fournodes in the directional-MANET frame structure shown in FIG. 3A, wherethe transmissions are made in accordance with a method of the presentdisclosure;

FIG. 3C is an exemplary schematic view of a directional-MANET framestructure in accordance with an aspect of the present disclosure, wherethe frame structure includes eight nodes, seven slots and fourtransmissions;

FIG. 3D is an exemplary schematic view of a directional-MANET framestructure in accordance with an aspect of the present disclosure, wherethe frame structure has ten nodes, eleven slots and five transmissions;

FIG. 4 is a flow chart showing a method of using a directional-MANETframe structure in accordance with an aspect of the present disclosure;

FIG. 5 is an exemplary graphical view of a transmission using adirectional MANET frame structure and method in accordance with anaspect of the present disclosure, where the system includes eight nodesand seven slots and showing the various transmissions when frequencydomain duplexing (FDD) is used;

FIG. 5A is an exemplary graphical view of a transmission using adirectional MANET frame structure and method in accordance with anaspect of the present disclosure, where the system includes fourteennodes in total, frequency domain duplexing (FDD) is used, and whereinphantom nodes are introduced in a first round of transmissions;

FIG. 5B is an exemplary graphical view of a transmission using adirectional MANET frame structure and method in accordance with anaspect of the present disclosure, where the system includes fourteennodes in total, frequency domain duplexing (FDD) is used, and whereinphantom nodes are introduced as needed;

FIG. 6A is an exemplary graphical view of a transmission using adirectional MANET frame structure and method in accordance with anaspect of the present disclosure, where the system includes nine nodesin total, frequency domain duplexing (FDD) is used, and wherein adecision to repartition smaller groups is made at a first opportunity;

FIG. 6B is an exemplary graphical view of a directional MANET framestructure and method in accordance with an aspect of the presentdisclosure, where the system includes nine nodes in total, frequencydomain duplexing (FDD) is used, and wherein a decision to repartitionsmaller groups is delayed until all groups are ready to berepartitioned; and

FIG. 6C is an exemplary graphical view of a directional MANET framestructure and method in accordance with an aspect of the presentdisclosure, where the system includes nine nodes in total, frequencydomain duplexing (FDD) is used, and wherein a decision to repartitionsmaller groups is deferred until all groups are of a same size.

Similar numbers refer to similar parts throughout the drawings.

DETAILED DESCRIPTION

A method for broadcasting information in a broadcast medium withdirectional coupling elements to that medium (e.g., antennas) isdescribed herein.

In certain embodiments of the present disclosure, the broadcast mediumcoupling could be completed via electromagnetic antennas. In otherembodiments the broadcast medium may be free space or air, or soundcoupling to air or water. The methods described herein could be coupledwith other methods as part of the “link” or media access control (“MAC”)protocols, or networking protocols in a system, but could potentially beimplemented at any layer of the ISO stack. While primarily intended forcommunications, the methods described herein could be used to controlaccess to a medium for a number of purposes including sensing themedium, navigation and ranging, to deny the use of the medium by a givenset of users, and the like.

FIGS. 1-1C show a PRIOR ART Omni MANET frame structure 100 and the wayin which frame structure 100 is used. FIG. 1 illustrates an Omni-MANETframe structure 100 in which omni-directional antenna are utilized. Anomni-directional antenna or omni-directional antenna is an antenna thatis capable of transmitting or receiving transmissions (particularlyradio transmissions) in all directions in one plane. The Omni MANETframe structure 100 comprises a broadcast control (BC) zone 102 and ademand access (DA) zone 104. Generally, a plurality of slots isallocated to the broadcast control (BC) zone 102. Each slot in zone 102will be referred to herein as a BC slot 103. Each BC slot 103 in zone102 is allocated to a specific node for broadcast traffic. Only thatspecific node can transmit during that slot and all other nodes will tryand receive that transmission. As illustrated in FIG. 1, four BC slots103 are shown, each having one specific node allocated therein, e.g.,Node 1 indicated by reference number 106 is in a first BC slot 103; Node2 indicated by reference number 108 is in a second BC slot 103, Node 3indicated by reference number 110 is in a third BC slot 103, and Node 4indicated by reference number 112 is in a fourth BC slot 103.

A separate zone 104 is allocated for “Demand Access”. Slots in zone 104are referred to herein as DA slots and are identified by the referencenumber 105. DA slots 105 in DA zone 104 are dynamically allocated asneeded to each node. A single DA slot 105 in DA zone 104 might be usedby multiple nodes to transmit if the transmissions do not interfere witheach other.

There are many algorithms or programs that may be used for allocatingslots for BC slots 103 and DA slots 105. An example program forallocating the DA slots 105 could be the well-known Unified SlotAssignment Protocol (USAP). An example method of allocating BC slots 103is that each possible node in the network has a slot allocated based onnode address. In some instances, allocating BC slots using ascendingorder from a start of a frame may be used. The frame structure 100 shownin FIG. 1 is a logical frame structure. In other embodiments, a “slotshuffling” program may be applied to pseudo-randomly reorder the slotsprior to actual transmission.

Even though each node broadcasts information in its dedicated slot, thisdoes not guarantee that all nodes hear all transmissions. As illustratedin FIG. 1A, first node 106 has a radio communications range 111A, secondnode 108 has a radio communications range 111B, third node 110 has aradio communications range 111C and fourth node 112 has a radiocommunications range 111D. The radio communications range 111D of fourthnode 112 is such that third node 110 can hear transmissions from thefourth node 112. However, first node 106 and second node 108 cannot heartransmissions from fourth node 112. First, second, and third nodes 106,108, 110 are all within communications range 111A, 111B, 111C of eachother and can always hear each other's transmissions. It will beunderstood that all nodes that are within radio communications range ofeach other (such as first, second and third nodes 106, 108, 110 in FIG.1A) hear each other's broadcast transmissions. This facilitatesmanagement of the MANET.

FIG. 1B, shows an Omni-MANET frame structure where there are four nodesin the network and each node is allocated a slot 103 in BC zone 102.Node 1, 106, is allocated a first BC slot 122, Node 2, 108, is allocateda second BC slot 124, Node 3, 110, is allocated a third BC slot 126, andNode 4, 112, is allocated a fourth BC slot 128. FIG. 1C shows that allfour nodes 106, 108, 110, 112 communicate with each othersimultaneously. These nodes 106-112 are in communications range of eachother and all nodes hear all other nodes transmissions.

FIGS. 2-2C show a PRIOR ART MANET laydown that utilizes directionalantenna. FIG. 2 illustrates a directional-MANET frame structure 200where each node uses a directional antenna. A directional antenna is anantenna that focuses its transmission or reception in a particulardirection. Frame structure 200 comprises a broadcast control (BC) zone202 and a demand access (DA) zone 204. Directional-MANET frame structure200 includes a plurality of BC slots 203 in BC zone 202 and a pluralityof DA slots 205 in DA zone 204.

Unlike the Omni-MANET 100 of FIGS. 1-1C, in the directional-MANET 200broadcasting information from one node to all neighbor nodes that are incommunications range is not always possible because of the directionalnature of the antenna used. As illustrated in FIG. 2A, when first node206 tries to broadcast to all nodes in communication range, first node206 must focus its beam 209 at a specific node, namely second node 208,such that other nodes i.e., third node 210 and fourth node 212, cannothear the first node's transmissions. This can cause a breakdown in theperformance of the MANET protocols that depend on all neighbor nodes incommunications range knowing, for example, the planned transmit scheduleof its neighbors.

One possible solutions to this problem is to allocate more transmitslots for each node to rebroadcast the same information for eachpossible destination node. So, for example, if there are four nodes 206,208, 210, 212, each node may be assigned three slots for BC traffic toensure the traffic reaches all possible neighbor nodes. With anomni-MANET (FIG. 1B), only four broadcast slots are required for allnodes to hear broadcasts from all possible other nodes. With the sameapproach, using the directional-MANET of FIG. 2B and replicating theinformation transmitted to each node, a total of twelve (four×three)slots are required for all broadcasts. This is shown in FIG. 2B, threeslots 220 in BC zone 202 in the directional-MANET frame structure 200are required for the broadcasts of “node 1→node 2,” “node 1→node 3,” and“node 1→node 4,” respectively. Three slots 222 in BC zone 202 arerequired for the broadcasts of “node 2→node 1,” “node 2→node 3,” and“node 2→node 4,” respectively. Three slots 224 in BC zone 202 arerequired for the broadcasts of “node 3→node 1,” “node 3→node 2,” and“node 3→node 4,” respectively. Finally, three slots 226 in BC zone 202are required for the broadcasts of “node 4→node 1,” “node 4→node 2,” and“node 4→node 3,” respectively. Thus, the number of slots required tobroadcast all information to all neighbor nodes is three times greaterthan when using omni-MANET 100 (FIG. 1B). In directional-MANET 200, notonly are more slots required to broadcast to all neighbor nodes than inomni-MANET 100 but the time required to make transmit the sameinformation to all neighbor nodes is also greater. Thus, using adirectional-MANET system is very inefficient. The inefficiency is evengreater in larger MANET systems.

FIGS. 3A-6C show a directional-MANET system in accordance with an aspectof the present disclosure. FIGS. 3A and 3B show an exemplary method ofbroadcasting using a directional-MANET in accordance with an aspect ofthe present disclosure. The provided directional-MANET of FIGS. 3A and3B is illustrated as a four node network, assuming that all four nodesare within communications range and must therefore hear each other'sbroadcasts. The method in accordance with the present disclosure takesadvantage of the fact that not all nodes can hear each other whendirectional antennas are used to allow multiple transmissions to occurat once. For cases where nodes have overlapping coverage and wouldinterfere, the network would depend on other techniques such as spreadspectrum or multi-user detection to resolve connection. Schedulingtechniques could also be applied.

FIG. 3A shows a directional-MANET frame structure 300 comprising abroadcasting control (BC) zone 302 and a demand access (DA) zone 304. Asillustrated, BC zone 302 includes six slots and MANET 300 includes fournodes.

In one embodiment of a method in accordance with an aspect of thepresent disclosure, the four nodes in the MANET 300 are ordered and forma first group. Any suitable manner of ordering the nodes in the networkmay be utilized. For example, the nodes may be ordered in the samemanner as indicated with respect to the omni-MANET 100. There are manyalgorithms or programs that may be used for allocating slots for BC zone302 and DA zone 304. An example program for allocating the DA slots inDA zone 304 could be according to the Unified Slot Assignment Protocol(USAP). An example method of allocating slots in BC zone 302 may includethat each of the four nodes in the network has a slot allocated based onthe node address. In particular, the BC slots may be allocated usingascending order from a start of a frame. In other embodiments, a “slotshuffling” program may be applied to pseudo-randomly reorder the slotsprior to actual transmission. In directional-MANET 300, the four nodesmay be ordered as Node 1, Node 2, Node 3, and Node 4, based on the nodesaddresses in ascending order and each of the Nodes 1-4 are allocatedinto BC slots based on their addresses.

In a next step according to an embodiment of the method of the presentdisclosure, the ordered four nodes are partitioned into a lower group306 and an upper group 308. The partition is based on the addresses ofthe nodes. So, Node 1 and Node 2 are partitioned into lower group 306and Node 3 and Node 4 are partitioned into upper group 308.

FIG. 3A shows a transmission (traffic) schedule 303 identifying a set ofdirectional transmissions to accomplish directional broadcast inaccordance with the method of the present disclosure. FIG. 3A shows afirst transmission 303A in which a first round of transmissions occursand a second transmission 303B in which a second round of transmissionsoccur. The set of transmissions are repeated in the BC zone 302 of eachframe.

FIGS. 3A and 3B show that the node with the lowest address in lowergroup 306 (Node 1) transmits its broadcast information to the node withthe lowest address in the upper group 308 (Node 3). As depicted in FIG.3B, this transmission activity is shown by arrow 305. An oval 310represents the orientation of node 1's directional antenna. In certainembodiments, node 3 would point its directional antenna towards node 1as appropriate. As shown in the transmission schedule 303 of FIG. 3A,the first transmission is notated as “node 1→node 3” in the firsttransmission 303A under Slot 1. Additionally, in the same Slot 1, thenode with the next lowest address in lower group 306 (Node 2)simultaneously transmits its broadcast information to the node with thenext lowest address in the upper group 308 (Node 4). As depicted in FIG.3B this simultaneous transmission activity is shown by arrow 307 and thesecond transmission 303B is noted as “node 2→node 4”. Additionally, asecond oval 312 represents the orientation of node 2's directionalantenna. In certain embodiments, node 4 would point its directionalantenna towards node 2 as appropriate. At this point, node 3 hasreceived node 1's broadcast information and node 4 has received node 2'sbroadcast information.

Then the transmission is reversed. As shown in Slot 2 of FIG. 3B, eventhough the same allocations are used, the directions of transmissionsare reversed so that the nodes in the upper group 308 transmit to thenodes in the lower group. In other words, node 3 and node 4 now transmitto node 1 and node 2, respectively. These transmissions are representedas “node 3→node 1” and “node 4→node 2” under Slot 2 in FIGS. 3A and 3B.After this transmission, node 1 has received node 3's broadcastinformation and node 2 has received node 4's broadcast information.

At this point in the method, node 1 has its own broadcast information aswell as node 3's broadcast information and vice versa. Similarly, node 2has its own broadcast information as well as node 4's broadcastinformation and vice versa. However, node 1 does not have node 4'sbroadcast information and vice versa and node 2 does not have node 3'sbroadcast information and vice versa.

At this point, all of the nodes in the lower group 306 and all of thenodes in the upper group have not yet communicated with each other. InSlot 3 of FIGS. 3A and 3B, each node talks to the next ascending addressin the other subgroup. For convenience, it may be considered that eachgroup is independently renumbered and given a different base address.So, in the case of node 1, this node would now talk to node (3+1) ornode 4. This may be thought of as having base value of 2, and being“node 2: in the group. The node value of 1 would be incremented and thenthe base value added. So node (1+1+2) or node 4. Node 2 would talk to(2+1) node 2 or 1 plus the base value of 2, or node 3. So, as shown inSlot 3 in FIGS. 3A and 3B, the lowest node in the lower group 306, whichis node 1, now talks to the highest node in the upper group 308, whichis node 4. Similarly, the highest node in the lower group 306, which isnode 2, now talks to the lowest node in the upper group 308 which isnode 3. These transmissions are represented as “node 1→node 4 and “node2→node 3” under Slot 3 of FIGS. 3A and 3B.

In Slot 4, the same allocations are used, however, the directions oftransmission is reversed such that node 4 and node 3 now transmit tonode 1 and node 2 respectively. These transmissions are represented as“node 4→node 1” and “node 3→node 2” under Slot 4 of FIGS. 3A and 3B. Atthe end of Slot 4, all nodes in the upper group 308 have receivedbroadcast information from all nodes in the lower group 306, and viceversa. However, not all nodes within the lower group 306 have heard fromthe other nodes in the lower group 306 and not all nodes within theupper group 308 have heard from the other nodes in the upper group 308.Thus, the same distribution process has to be repeated to createsubgroups within the lower group 306 and within the upper group 308. So,lower group 306 is divided into two new subgroups: a first lower group306A and a first upper group 306B, with the lower addressed nodes goinginto the first lower group 306A and the higher addressed nodes goinginto the first upper group 306B. As shown in FIG. 3B, node 1 goes intothe first lower group 306A and node 2 goes into the first upper group306B. Similarly, the original upper group 308 is divided into two newsubgroups: a second lower group 308A and a second upper group 308B. Node3 goes into the second lower group 308A and node 4 goes into the secondupper group 308B. Then, the same program is applied as before with thesesubgroups simultaneously. First lower group 306A talks to first uppergroup 306B and second lower group 308A talks to second upper group 308B.Since there is only one node in each group, only one slot is required todo this transmission. Thus, schematically, these transmissions may berepresented as “node 1→node 2” and “node 3→node 4” under Slot 5 of FIGS.3A and 3B. In Slot 6, the direction of transmission is reversed but thesame participants communicate with each other. Thus, schematically,these transmissions may be represented as “node 2→node 1” and “node4→node 3” under Slot 6 of FIGS. 3A and 3B. At this point, all nodes inthe network possess the broadcast information of all other nodes in thenetwork and the transmission is completed.

It should be noted that unlike the PRIOR ART directional-MANET 200, thedirectional-MANET 300 of the present disclosure requires only six slotsto complete the transmission whereas MANET 200 required twelve slots.Thus the number of slots and the time taken to broadcast information toall nodes in the network is substantially reduced.

In another embodiment (not illustrated herein) if bidirectionalcommunication method is available (i.e., frequency domain duplexing,FDD), then Slot 1 and Slot 2 may be combined into a single slot and thesame set of transmission information exchanges as illustrated in FIGS.3A and 3B may occur. So, for example, the first transmission 303A underSlot 1 “node 1→node 3” and the first transmission 303A under Slot 2“node 3→node 1”, may be replaced by a single slot in which thetransmissions “node 1←→node 3” will occur as the nodes simultaneouslybroadcast their information to each other. Similarly, in the secondtransmission 303B, nodes 2 and 4 will broadcast their informationsimultaneously to each other. Similarly, Slot 3 and Slot 4 may becombined into a single slot and the transmissions in the combined slotmay occur simultaneously, i.e., node 1←→node 4 and node 2←→node 3.Finally, Slot 5 and Slot 6 may be combined into a single slot and thetransmissions node 1←→node 2 and node 3←→node 4 will occursimultaneously. When FDD is used, the lowest addressed node may use thelowest frequency for transmission in the frequency pair used forduplexing transmission. However, other alternative methods for assigningthe frequencies in FDD are also possible. Thus, if the method inaccordance with the present disclosure is used and FDD is utilized, onlythree slots will be required. The PRIOR ART Omni-MANET 100 requires fourslots (one for each node as shown in FIG. 1C) to achieve the samebroadcasting function. Thus, the directional broadcast program describedherein is more efficient than the PRIOR ART Omni-MANET system when FDDis used.

In another embodiment, as shown in FIG. 3C, there may be eight nodes inthe network and seven slots and a transmission schedule 303. Thetransmission schedule 303 identifies a set of directional transmissionsto accomplish directional broadcasting for all nodes withincommunications range. Because there will be four nodes in the lowergroup and four nodes in the upper group, in each slot, the transmissionschedule 303 require four transmissions, namely, a first transmission303A, a second transmission 303B, a third transmission 303C, and afourth transmission 303D. So, for example if the eight nodes compriseNode 1, Node 2, Node 3, Node 4, Node 5, Node 6, Node 7 and Node 8, thestep of partitioning the nodes would divide the nodes into a lower group(Nodes 1, 2, 3 and 4) and an upper group (Nodes 5, 6, 7 and 8). Node 1will transmit to Node 5 in first transmission 303A; Node 2 will transmitto node 6 in second transmission 303B, node 3 will transmit to node 7 inthird transmission 303C and node 4 will transmit to node 8 in fourthtransmission 303D. The transmission schedule 303 may be repeated in anumber of slots in the BC zone 302 of frame structure 300.

In another embodiment, as shown in FIG. 3D, if there are ten nodes inthe network, then the transmission schedule 303 may comprise a firsttransmission 303A, a second transmission 303B, a third transmission303C, a fourth transmission 303D, and a fifth transmission 303E. Thefifth transmission 303E may be used for phantom nodes which will bedisclosed in details later in this disclosure.

FIG. 4 illustrates the method 400 to implement the directionalbroadcasting algorithm or program in accordance with the presentdisclosure. The method 400 comprises the following steps:

(1) step 401—providing a MANET that includes nodes, slots and usesdirectional antenna;

(2) step 402—ordering all nodes in the network by address forming afirst group and allocating a total number of slots in the network;

(3) step 404—partitioning each group into two subgroups by address; i.e.forming a Lower subgroup and an Upper subgroup;

(4) step 406—each node in the Lower subgroup partition transmits to acorresponding node in the Upper subgroup partition (If there aremultiple groups they may transmit simultaneously);

(5) step 408—reversing the direction of transmission for each node pair(if the transmissions were not simultaneous frequency domain duplexing(FDD))—i.e. each node in the Upper subgroup partition transmits to thecorresponding node in the Lower subgroup partition;

(6) step 410—verify that all nodes in the Lower subgroup partitioncommunicated with all nodes in the Upper subgroup partition;

(7) step 412—if the answer to the verification of step 410 is “NO” thenall the groups are permuted. This ensures that the nodes in the lowergroup will communicate with different nodes in the upper group than wasthe case in the previous round of transmissions. Once one or both of thelower and upper groups are permuted, the steps 406 to 410 are repeated;and

(8) step 414—if the answer to the verification of step 410 is “YES” thenverification is made as to whether there is only 1 node per group. Ifthe answer is “NO” then steps 404 to 414 are repeated. If the answer is“YES” then the transmission process ends.

The method 400 will be described in greater detail hereafter. Step 401requires providing a directional MANET that includes a certain number ofnodes and slots and uses at least some directional antenna. This stepmay be seen in FIG. 3A as providing a frame structure for directionalMANET 300 with four nodes and six slots and the nodes use directionalantenna.

In step 402 all possible nodes that may participate in the network aredetermined and then those determined nodes are placed in an order, suchas by using their addresses. In some embodiments, the maximum number ofnodes in the network (such as network 300) may be dynamicallydetermined. As long as this maximum number of nodes is determined thesame way in all nodes of the network and the addresses of potentiallyparticipating nodes are known, method 400 may be implemented. It shouldbe noted that any method of allocating addresses for all nodes may beused. Each node in the network requires a unique address or if there isanother unique parameter associated with each node, then that uniqueparameter may be used instead of an address provided that the values areknown to all participants and the parameter allows the nodes to beuniquely ordered. The term “address” as used herein should be understoodto include ordering the node participants using any unique parameters.Referring back to FIGS. 3A and 3B, this step may be seen where the nodesare ordered as by ascending address as node 1, node 2, node 3 and node4.

Once the number and the order of the participating nodes is established,the number of slots required to implement the directional broadcastmethod may be determined and allocated in any suitable manner.(Referring back to FIGS. 3A and 3B, since four nodes are participating,six slots are allocated.) In other embodiments, the maximum number ofaddresses may be pre-computed and the appropriate number of slots tosupport that number of addresses may be allocated. For example, if thereare 16 nodes, then 15 slots are required when operating in FDD. In otherembodiments, the allocation could be static rather than dynamic. Instatic allocation, every frame is fixed or possibly distributed over asubset of frames if a “superframe” structure is used where only someframes include a broadcast zone on a repeating schedule or each frame inthe superframe only contains a portion of the total BC zone.

As shown at step 404 in FIG. 4, the method 400 then partitions the nodesin half based on the addresses with all the lower addresses going to onegroup (i.e., a lower group) and the upper addresses going to anothergroup (i.e., a upper group). Referring back to FIGS. 3A and 3B, thelower addressed nodes, node 1 and node 2, are placed in the lower group306; and the higher addressed nodes, nodes 3 and node 4 are placed inthe upper group 308.

In one embodiment, the total number of nodes is an even number and thetwo groups (lower and upper) are of equal size. In another example, ifthe total number of nodes is an odd number then the two groups are notof the same size. When there is odd number of nodes in the network thenthe extra node is assigned to the lower group and a “phantom” node iscreated in the upper group so that the two groups are of the same size.The phantom node is paired with the extra node in the lower group.(Other solutions to the different numbers of nodes in the two groups maybe applied such as assigning the phantom node to the lower group, forinstance to the lowest address in the lower group; or by assigning thephantom node to any address in either of the upper or lower group.) Allthat is required is that the phantom nodes are consistently placed thesame way by all nodes in the group. For example, if there are ninenodes, then the highest node in the lower group will be node 5. Sincethe total number of nodes is odd, node 5 would not have anyone tobroadcast its information to so a phantom node is created and assignedto the highest address in the upper group so that node 5 can transmitits information to the phantom node. Since the phantom node does notactually exist, node 5 need not transmit to or receive from the phantomnode. Node 5 can do some other activity as long as that activity doesnot interfere with broadcasts from the other nodes. In other words, thephantom node is purely for bookkeeping. In certain embodiments, if therewere only three nodes then a phantom node (node 4) would be created andthe same transmission pattern as illustrated in FIGS. 3A and 3B would beused. When node 4 is scheduled to transmit, no transmission would occur,and the intended receiver (such as node 2) would not need to listen fora transmission from node 4. If there were other nodes in the lowergroup, additional transmissions would be scheduled in Slot 1 such thatall nodes in the lower group would transmit if there is a correspondingnode in the upper group to receive. In Slot 2, the same allocationswould be used but this time with the direction of transmission reversed.

As depicted at step 406 in FIG. 4, once two groups (the lower group andthe upper group) are formed, the lowest address in the lower group firsttransmits its information to the lowest address in the upper group.Then, the second lowest address in the lower group transmits itsinformation to the second lowest address in the upper group. (Referringto FIG. 3A by way of example, node 1 transmits to node 3 and node 2transmits to node 4.) This same process continues until the last addressin the lowest group transmits its information to the last address in theupper group. In another instances, all the nodes in the lower group maytransmit their information simultaneously to the corresponding nodes inthe upper group. This transmission would occupy a first slot in thenetwork (such as Slot 1 in FIG. 3A).

As depicted at step 408 in FIG. 4, the node pairs from step 406 aremaintained, but the direction of transmission is reversed so that thenodes in the upper group now transmit information to the lower group.This requires a second slot in the network. So, for example, in FIGS. 3Aand 3B, node 3 transmits to node 1 and node 4 transmits to node 2 inSlot 2. If the nodes are capable of full duplex communications (i.e.,frequency domain duplexing, FDD), then a single slot is sufficient toaccomplish both steps. Thus, step 408 may be combined with step 406.Using FDD to combine step 408 with step 406 is a preferredimplementation of the method, but it is not required to practice themethod to accomplish the same purpose.

As shown at step 410 in FIG. 4, the next step in method 400 checks orverifies whether all nodes in the lower group have exchanged their datawith all nodes in the upper group. If all of the nodes in the lowergroup have not exchanged their data with all of the nodes in the uppergroup, then the method continues to step 412 which requires permutationof the lower and upper groups relative to each other. So, once thelowest nodes in the two groups have exchanged information then thelowest node in the lower group will transmit to the next lowest node(i.e., the second lowest) in the upper group. The second lowest addressin the lower group will transmit to the third lowest node in the uppergroup and so on. This would be a “permutation” or the original set oftransmitters. In certain embodiments, the target node in the upper groupis computed using modulo arithmetic, such that the highest node in thelower group transmits to the lowest mode in the upper group on the firstpermutation and vice versa in step 412. The number of permutations maybe determined by ceil(M/2), where M is the largest number of nodes inany set for that round. Particularly, the number may include a phantomnode if necessary. For instance, when there are seven nodes, then thelargest number of nodes in the set is 8. Thus, the required number ofpermutations is 4.

Alternatively, any methods for permuting the groups may be used so thatall nodes in the lower group communicate exactly once with all of thenodes in the upper group.

After the groups are permuted, the method 400 proceeds back to steps 406and 408 where the nodes in the lower group transmit information to thenodes in the upper group and vice versa. So, for example, in FIGS. 3Aand 3B, node 1 transmits to node 4 and node 2 transmits to node 3; andthen the transmission is reversed and node 4 transmits to node 1 andnode 3 transmits to node 2. As described previously, two slots may betaken for each pair of nodes to exchange their information. If FDD isused, it may only require only one slot to accomplish the same. One ormore phantom nodes may exist as the highest node in the upper group orthe lowest node in the lower group for bookkeeping purposes. Whenphantom nodes exist, nodes that must transmit to the phantom node neednot actually transmit/receive to the phantom node during those slots butmay conduct some other activity as long as that activity does notinterfere with the other broadcasts. This is also true for nodeaddresses that are allocated but it is known that the nodes are notcurrently available in the network to transmit or receive broadcasts.Steps 406, 408. 410, 412 will continue until all of the nodes in thelower group have transmitted to all of the nodes in the upper group andvice versa. So if there were 2̂n nodes (n>2) in all 2̂n slots will havebeen consumed (2̂(n−1) if FDD). In certain embodiments, once introduced,the phantom nodes (and their addresses) are maintained through allfuture iterations until all iterations are complete. At this point,since all of the nodes in the lower group have transmitted all theirinformation to all of the nodes in the upper group, the answer for thequestion in step 410 will be “Yes.” Then, the method 400 proceeds tostep 414 as shown in FIG. 4.

At step 414 in FIG. 4, the method 400 asks whether there is only onenode remaining in each group. If either of the groups includes more thanone node, then each of the groups must be broken into subgroups, and themethod then reverts to step 404 and the process is repeated. In thesecond iteration (partition) of step 404, the lower group may be dividedinto two subgroups: a first lower subgroup (L1) and a first uppersubgroup (U1). Similarly, the upper group is divided into two subgroups:a second lower subgroup (L2) and a second upper subgroup (U2). This isillustrated in FIG. 3B in Slot 5 where the lower group 306 (whichincludes nodes 1 and 2) become first lower subgroup 306A (node 1) andfirst upper subgroup 306B (node 2); and upper group 308 (which includesnodes 3 and 4) become second lower subgroup 308A (node 3) and secondupper subgroup 308B (node 4). Then, the same method may be applied toeach of these subgroups so that all of the nodes in the first lowersubgroup (L1) transmit to all of the nodes in the first upper subgroup(U1) and vice versa. Similarly, all nodes in the second lower subgroup(L2) would transmit to all nodes in the second upper subgroup (U2) andvice versa. Referring again to FIG. 3B, node 1 transmits to node 2 andvice versa; and node 3 transmits to node 4 and vice versa.

In certain embodiments, steps 406 to 412 may include multiple upper andlower groups in an iteration and the steps apply simultaneously to allpairs of upper and lower groups. In the first iteration there is onepair of groups; in the second iteration two pairs, in the thirditeration four pairs, and so on. Since there are less nodes in eachsubgroup as the iterations continue, it will take less slots to completethe transmissions required at each iteration. In certain embodiments, ifthere were 2̂ nodes originally, then this set of transmissions would take2̂(n−1) slots on the second iteration or 2̂(n−2) slots for FDD. If thereis more than one node in each of the subgroups, the process will berepeated with each subgroup again being broken into lower and uppersubgroups. So, where there were two groups in the first iteration andfour groups in the second iteration, there would be eight groups in thethird iteration, and so on. Each time the number of slots required forexchanges would decrease by roughly a factor of two until only one nodeexists in each subgroup. After the nodes in the upper and lowersubgroups at the lowest tier (e.g. with one node each) exchangebroadcasts, as shown at step 414, the method would terminate with allnodes have broadcasted to all other nodes in the network.

The number of iterations (partitions) is determined by ceil(Log₂(N)),where N is the number of nodes, Log₂ is a log base 2, and ceil is thesmallest integer larger than the argument. For instance, if there are 8nodes, then 3 iterations (partitions) are required to accomplish themethod. This is graphically illustrated in FIG. 5. Particularly, asshown in FIG. 5, after each iteration (partition), the number of groupsincreases by a factor of two because each group is divided into twosubgroups. Thus, after the first iteration (partition) 314, there aretwo groups. After the second iteration (partition) 316, there are fourgroups. After the third iteration (partition) 318, there are eightgroups. Since there are less nodes in each subgroup as the iterationscontinue, it will take less slots to complete the transmissions requiredat each iteration. Each time the number of slots required to exchangedata would decrease by roughly a factor of two until only one nodeexists in each subgroup. When each group has one node, as shown at step414 in FIG. 4, the method would be terminated with all nodes havingbroadcasted to all of the other nodes in the network.

Generally, when there are a total number nodes (N) which is equivalentto power of 2 (2^(n)) (i.e., N=2, 4, 8, 16, 32, 64 etc.), then 2*(N−1)slots are required to complete all transmissions so that all nodes hearbroadcasts from all of the other nodes if they are in communicationsrange. In one instance, if there is a total of two nodes, then thereshould be at least two slots to complete all transmissions. In anotherinstance, if there is a total of four nodes, then there should be sixslots to complete all transmissions. In another instance, if there isthe total of eight nodes, then there should be at least fourteen slots.However, when frequency domain duplexing (FDD) is used, then the totalnumber of slots become N−1 so that one slot is required for two nodes,three slots are required for four nodes, and seven slots are requiredfor eight nodes, respectively.

Furthermore, if there are a total number of nodes (N) where the totalnumber of nodes are more than 2^((n−1)) but less than 2^(n) with n beingthe integer, then the total number of required slots is bounded by2*N+2*ceil(Log₂(N)), where N is the number of nodes, Log₂ is a log base2, and ceil is the smallest integer larger than the argument. Forexample, if the total numbers of nodes are five, six and seven which arebetween four and eight (Le., n=3), the maximum total number of slots maybe 16, 18, and 20, respectively. When frequency domain duplexing (FDD)is used, the total number of slots become N+ceil(Log₂(N)). Thus, for aspecific maximum number of nodes in a network, the exact number of slotsrequired may be pre-computed.

However, the maximum total number of slots may be varied depending onhow many phantom nodes must be introduced and when the phantom nodes areintroduced. Numbers of phantom nodes may be introduced in the firstround of transmissions of each iteration (partition) to get the totalnumber of nodes to be equal to a power 2. Alternatively, a number ofphantom nodes may be introduced as needed during the process. Forexample, as depicted in FIG. 5A, when there are a total of 14 nodes, twophantom nodes (P15 and P16) may be introduced at the first slot (i.e.,“Slot 1”) to get the total number of nodes to be 16 which is within apower 2 (i.e., 2⁴). Alternatively, as depicted in FIG. 5B, two phantomnodes (P08 and P15) may be introduced at the eighth slot (i.e., “Slot8”). Generally, introducing phantom nodes in the first round is lessefficient than introducing phantom nodes as they are needed.

FIG. 6A is an exemplary graphical view of a transmission using adirectional MANET frame structure and method in accordance with anaspect of the present disclosure, where the system includes nine nodesin total, frequency domain duplexing (FDD) is used, and wherein adecision to repartition smaller groups is made at a first opportunity.FIG. 6B is an exemplary graphical view of a directional MANET framestructure and method in accordance with an aspect of the presentdisclosure, where the system includes nine nodes in total, frequencydomain duplexing (FDD) is used, and wherein a decision to repartitionsmaller groups is delayed until all groups are ready to berepartitioned. FIG. 6C is an exemplary graphical view of a directionalMANET frame structure and method in accordance with an aspect of thepresent disclosure, where the system includes nine nodes in total,frequency domain duplexing (FDD) is used, and wherein a decision torepartition smaller groups is deferred until all groups are of a samesize.

As indicated above, the decision to repartition a smaller group may bedelayed until all of the current groups are ready to be repartitioned(as shown in FIG. 6B) or may be made at the first opportunity (as shownin FIG. 6A). As shown in FIG. 6A, repartitioning groups may be madeafter the seventh slot (i.e., “Slot 7”) when the second lower subgroup(L2) and the second upper subgroup (U2) have their first opportunity tobe repartitioned. Alternatively, as depicted in FIG. 6B repartitioningthe second lower subgroup (L2) and the second upper subgroup (U2) may bedelayed until the ninth slot (i.e., “Slot 9”). As shown in FIGS. 6A-6C,a first phantom node P10 is first introduced in Slot 1, a second phantomnode P06 is first introduced in Slot 6, and a third phantom node P04 isfirst introduced in Slot 9.

When partitioning results in two different group sizes, the decision torepartition a smaller group may be deferred until all of the groups areof the same. As shown in FIG. 6A, the transmission between node 6 tonode 7 as well as between node 8 and node 9 are implemented in Slot 8.However, the first lower group L1 and the upper group U1 have six nodes,and the third lower group L3 and the third upper group U3 and the fourthlower group L4 and the upper group U4 have two nodes, respectively.Thus, the transmission between node 6 and node 7 as well as thetransmission between node 8 and node 9 may occur in any of Slot 8, Slot9, Slot 10, and Slot 11.

While the method is useful for broadcasting information in a network ofnodes with directional antennas, it can also be advantageously combinedwith other methods. For example, if some nodes have omni-directionalantennas, and some nodes have directional antennas, it is useful for thenodes with omni-directional antennas to be allocated separately and nothave them participate in the directional broadcasting program. Instead,each omni node would be allocated a dedicated slot as part of the BCzone and all directional nodes would position their antennas to try toreceive from the omni node during that slot.

In certain embodiments, it is often useful to partition networks intosubnets where a reduced number of nodes directly communicate to eachother in each subnet. In such cases a gateway node can rebroadcastinformation from one subnet to another and vice versa. The gatewayapproach may be combined with the directional broadcasting approach toallow operations across subnets.

Also, there may be cases where because of node alignments withdirectional antennas, transmissions from multiple nodes are receivedsimultaneously at a single receiver. Such situations may be resolved forinstance by applying spread spectrum or multi-user detection techniques.Scheduling techniques can also be applied such as having nodessystematically defer to each other when they detect a potential conflictat a receiver. So if two nodes recognize that their transmissions willoverlap for a given receiver, the higher address node would defer on oddframes, and the lower address would defer on even frames. If no extraslots are allocated, this would result in a reduced (but oftenacceptable) rate of broadcast for the impacted nodes. Alternatively,deferral slots could be added at the end of the BC that would be used asneeded such that the deferring nodes are not necessarily penalized inbroadcast throughput.

In the foregoing description, certain terms have been used for brevity,clearness, and understanding. No unnecessary limitations are to beimplied therefrom beyond the requirement of the prior art because suchterms are used for descriptive purposes and are intended to be broadlyconstrued.

Moreover, the description and illustration set out herein are an exampleand the disclosure is not limited to the exact details shown ordescribed.

What is claimed:
 1. A method of broadcasting information in a networkcomprising: providing a Mobile Ad-hoc Network (MANET) that includes aplurality of nodes, wherein at least some of the nodes use a directionalantenna; ordering the plurality of nodes in the MANET; partitioning theplurality of nodes into a first group of nodes and a second group ofnodes; transmitting information from each node in the first group ofnodes to a corresponding node in the second group of nodes; andreversing direction of transmitting by transmitting information fromeach node in the second group of nodes to a corresponding node in thefirst group of nodes.
 2. The method of claim 1, wherein the step ofordering the nodes includes ordering the nodes by address.
 3. The methodof claim 2, wherein the step of ordering by address includes placinglower address nodes into the first group of nodes and placing higheraddress nodes into the second group of nodes.
 4. The method of claim 2,wherein the step of ordering the nodes by address includes ordering theaddresses in ascending order.
 5. The method of claim 1, furthercomprising allocating slots in the network.
 6. The method of claim 5,further comprising determining an order of transmission from the slots.7. The method of claim 1, wherein the step of transmitting informationbetween each node in the first group of nodes and the correspondingnodes in the second group of nodes occurs simultaneously.
 8. The methodof claim 1, further comprising: verifying that all nodes in the firstgroup of nodes have communicated with all nodes in the second group ofnodes.
 9. The method of claim 8, further comprising: permuting the firstgroup of nodes and the second group of nodes if all nodes in the firstgroup of nodes have not communicated with all nodes in the second groupof nodes.
 10. The method of claim 9, further comprising: repeating thesteps of transmitting information from each node in the first group ofnodes to a corresponding node in the second group of nodes; reversingthe direction of transmitting and verifying that all nodes in the firstgroup of nodes have communicated with all nodes in the second group ofnodes until all nodes in the first group of nodes have communicated withall nodes in the second group of nodes.
 11. The method of claim 8,further comprising: verifying that there is only one node in each of thefirst group of nodes and each of the second group of nodes after thestep of verifying that all of the nodes in the first group of nodes havecommunicated with all of the nodes in the second group of nodes.
 12. Themethod of claim 11, further comprising: repartitioning the first groupof nodes into a first subgroup of nodes and a second subgroup of nodesand repartitioning the second group of nodes into a third subgroup ofnodes and a fourth subgroup of nodes when the first group of nodes orthe second group of nodes includes more than one node.
 13. The method ofclaim 12, wherein the step of repartitioning occurs when the step ofpermutation is ended.
 14. The method of claim 1, wherein the step ofpartitioning the nodes into the first group of nodes and the secondgroup of nodes includes providing at least one phantom node.
 15. Themethod of claim 14, wherein the step of providing at least one phantomnode occurs when a total number of the nodes in the first group of nodesor the second group of nodes is an odd number.
 16. The method of claim14, wherein the step of providing the at least one phantom node isundertaken to provide a total number of nodes equal to a power of two.17. The method of claim 14, the step of providing at least one phantomnode is further accomplished by providing the least phantom nodes asneeded.
 18. The method of claim 1, wherein the MANET includes oneomni-directional antenna.
 19. A method of broadcasting information in anetwork comprising: providing a Mobile Ad-hoc Network (MANET) thatincludes nodes, wherein at least some of the nodes use a directionalantenna; ordering the nodes in the MANET; determining a total number ofthe nodes; partitioning the nodes into a first group of nodes and asecond group of nodes; transmitting information from each node in thefirst group of nodes to a corresponding node in the second group ofnodes; reversing direction of transmitting by transmitting informationfrom each node in the second group of nodes to a corresponding node inthe first group of nodes; verifying that all nodes in the first group ofnodes have communicated with all nodes in the second group of nodes;permuting the first group of nodes and the second group of nodes if allnodes in the first group of nodes have not communicated with all nodesin the second group of nodes; repeating the steps of transmittinginformation from each node in the first group of nodes to acorresponding node in the second group of nodes; reversing the directionof transmitting and verifying that all nodes in the first group of nodeshave communicated with all nodes in the second group of nodes until allnodes in the first group of nodes have communicated with all nodes inthe second group of nodes; and verifying that there is only one node ineach of the first group of nodes and each of the second group of nodesafter the step of verifying that all the nodes in the first group ofnodes have communicated with all of the nodes in the second group ofnodes.
 20. The method of claim 19, wherein every node in the MANET usesa directional antenna.